Article Six barred new heavy cruisers and light cruisers exceeding 8,000 tons before 1 January 1943. A party whose national security was materially affected by another power's actual or authorized construction could invoke an exception. It had to notify the other parties of its intentions and reasons, after which it could build cruisers of up to 10,000 tons. The other treaty parties could then exercise the same right. The temporary restrictions created no commitment to continue them after 1942.
Notable Point · 30:09-31:46
How the cruiser escalator clause could restore a 10,000-ton limit
Security concerns arising from another power's construction could release treaty parties from the temporary cruiser restrictions.